/*
 * Copyright (C) 2017-2019 Dremio Corporation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.dremio.concurrent;

import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Ensures no more than a single copy of this runnable is run at any one time.
 */
public class SingletonRunnable implements Runnable {
  private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(SingletonRunnable.class);

  private final Runnable delegate;
  private final AtomicBoolean running = new AtomicBoolean(false);

  public SingletonRunnable(Runnable runnable) {
    this.delegate = runnable;
  }

  @Override
  public void run() {
    if(!running.compareAndSet(false, true)) {
      logger.info("Task {} already running, skipping secondary execution.", delegate.toString());
      return;
    }

    try {
      delegate.run();
    } finally {
      running.compareAndSet(true, false);
    }
  }

  @Override
  public String toString() {
    return delegate.toString();
  }

  public static Runnable of(final Runnable delegate, final String name) {
    return new SingletonRunnable(delegate);
  }

}
